In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks is also called a “NodeB”. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions of the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units (UEs).
In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. One result of the forum's work is the High Speed Packet Access (HSPA).
In a High Speed Packet Access (HSPA) network, a wireless terminal is connected to a serving cell. The serving cell is responsible for the data scheduling for the wireless terminal. The wireless terminal, alternately referred to as a user equipment unit (UE), may also be connected to one or more non-serving cells. The serving cell and any non-serving cells to which the wireless terminal is connected collectively make up the active set for the wireless terminal.
In a HSPA network a serving cell is under the control of a base station (NodeB) that is here referred to as the serving NodeB. Likewise, other NodeBs controlling non-serving cells in the active set can be referred to as non-serving NodeBs. Just like the serving NodeB, the non-serving NodeBs are able to receive uplink data transmissions from the wireless terminal (UE), and the fact that they are able to do so provides a so-called soft handover gain. The non-serving NodeBs are also able to moderate the transmissions from the wireless terminal (UE) through transmit power control (TPC) commands and relative grants (RG) in order to avoid too large inter-cell interference from the wireless terminal (UE) towards cells controlled by the non-serving NodeBs.
High Speed Downlink Packet Access (HSDPA) for the downlink was introduced in 3GPP WCDMA specification Release 5. Multi-carrier High Speed Downlink Packet Access (MC-HSDPA) comprises simultaneous High Speed Downlink Packet Access (HSDPA) transmission over more than one downlink carrier to a wireless terminal (UE).
The High Speed Downlink Packet Access (HSDPA) was followed by introduction of High Speed Uplink Packet Access (HSUPA) with its Enhanced Dedicated Channel (E-DCH) in the uplink in 3GPP WCDMA specification Release 6. HSUPA uses its uplink enhanced dedicated channel (E-DCH) for its E-DCH employs link adaptation methods similar to those employed by HSDPA. In its scheduled mode HSUPA uses a packet scheduler (similar to HSDPA), but also operates on a request-grant procedure. According to request-grant procedure, wireless terminals individually request permission to send data. In response to such requests, the scheduler at the NodeB decides when and how many wireless terminals will be allowed to do so. A request for transmission contains data about the wireless terminal, e.g., the state of the transmission buffer and the queue and the wireless terminal's available power margin. In addition to its scheduled mode of transmission, for HSUPA the standards also allows a self-initiated transmission mode from the UEs, denoted non-scheduled.
At Layer 1, HSUPA introduces new physical channels E-AGCH (Absolute Grant Channel), E-RGCH (Relative Grant Channel), F-DPCH (Fractional-DPCH), E-HICH (E-DCH Hybrid ARQ Indicator Channel), E-DPCCH (E-DCH Dedicated Physical Control Channel) and E-DPDCH (E-DCH Dedicated Physical Data Channel). E-DPDCH is used to carry the E-DCH Transport Channel; E-DPCCH is used to carry the control information associated with the E-DCH.
Multi-carrier High Speed Downlink Packet Access (MC-HSDPA) has been introduced in 3GPP Release 8. As a next step, multi-carrier High Speed Uplink Packet Access (MC-HSUPA) has been proposed to be included in 3GPP Release 9. Multi-carrier High Speed Packet Access (MC-HSPA) is described, e.g., in Johansson, Klas, et al., “Multi-Carrier HSPA Evolution”; http://www.ericsson.com/technology/research_papers/atsp/doc/multi-carrier_hspa_evolution.pdf, 2009, incorporated herein by reference in its entirety. While multi-carrier transmission does not increase “spectral efficiency” of a system (maximum achievable throughput [bps/cell/Hz]), the experienced user data rates are likely to increase significantly, in particular for bursty packet data traffic at low and moderate load. Moreover, by exploiting a wider bandwidth per connection, power inefficient higher order modulation schemes can be avoided, and the practical as well as theoretical peak data rate of the system are increased.